Set SDKROOT to empty string to make builds work with Carthage

Author: hamchapman

PusherSwift/PusherSwift.xcodeproj/project.pbxproj

@@ -389,7 +389,7 @@
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				ONLY_ACTIVE_ARCH = YES;
-				SDKROOT = iphoneos;
+				SDKROOT = "";
 			};
 			name = Debug;
 		};
@@ -415,7 +415,7 @@
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
-				SDKROOT = iphoneos;
+				SDKROOT = "";
 				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";
 			};
 			name = Release;
@@ -471,7 +471,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.pusher.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = PusherSwift;
 				PROVISIONING_PROFILE = "";
-				SDKROOT = iphoneos;
+				SDKROOT = "";
 				SKIP_INSTALL = YES;
 				SUPPORTED_PLATFORMS = "iphonesimulator iphoneos macosx appletvsimulator appletvos";
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
@@ -527,7 +527,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "com.pusher.$(PRODUCT_NAME:rfc1034identifier)";
 				PRODUCT_NAME = PusherSwift;
 				PROVISIONING_PROFILE = "";
-				SDKROOT = iphoneos;
+				SDKROOT = "";
 				SKIP_INSTALL = YES;
 				SUPPORTED_PLATFORMS = "iphonesimulator iphoneos macosx appletvsimulator appletvos";
 				SWIFT_VERSION = 3.0;